Cyclopentanophenanthrene derivatives and method for preparation thereof



United States Patent CYCLOPENTANOPHENANTHRENE DERIVATIVES AND METHOD FOR PREPARATION THEREOF Carl Djerassi, Birmingham, Mich., and George Rosenkranz, Mexico City, Mexico, assignors, by mesne assignments, to Syntex S. A., Mexico City, Mexico, a corporation of Mexico Application September 3, 1952, Serial No. 307,722

Claims priority, application Mexico September 20, 1951 2 Claims. (Cl. 260 -39745) No Drawing.

The present invention relates to novel cyclopentanophenanthrene derivatives and to a method for the preparation thereof. More particularly, the present invention relates to certain novel intermediates useful for the preparation of allopregnane-17a, 21-diol-3,11,20-trione (dihydroallocortisone) which can be readily converted to cortisone in accordance with our United States application, Serial Number 218,095, filed March 28, 1951, and i to a novel process for the preparation thereof.

In our United States application, Serial Number 291,556, filed June 3, 1952, there is disclosed a method for the preparation of 3/8, llu-dihydroxy sapogenins stene-3 8, 11a, 26-triol which on oxidation with chromic anhydride under the conditions set forth in our United States application, Serial Number 287,821, filed May 14, 1952, can be degraded to A -allopregnene-iifl, llcc-diOl diacetate.

It has been fourther discovered, in accordance with the present invention, that hydrogenation of the l617 double bond of the last mentioned compound gives a corresponding saturated allopregnane compound and that this compound may be readily converted as hereinafter set forth into the corresponding allopregnane-3fl, 11a,

It has further been discovered in accordance with the present invention, that the last mentioned triol may be converted into allopregnan-f'afi, 17a-dio1-11, ZO-dione which may readily be converted into dihydroallocortisone as has already been described in the application of Rosenkranz, Pataki and Djerassi, Serial Number 288,311, filed May 16, 1952. In the alternative, the allopregnam' triolone can be brominated with one mol of bromine to give the corresponding 21-bromo derivative which is thereafter converted into the 21-monoacetate which may thereafter be oxidized with a mild oxidizing agent to form dihydroallocortisone.

The production of allopregnan-lip, 11a, 17a-triol-20- one from 22-isoallospirostan-3p, lla-diol may be illustrated by the following formula:

I 0 CH OAQ 7 H0 fi Acetic anhydride o Ho 200 0. A00

, Oxidation l Chromic anhydride an 7 mild saponification on; 1H, C=0 C=0 7 AcO- from a A -sapogenin such as A -2Z-iSoallospirostene-Sfl, 11m-diol-7-one. a i

In accordance with the present invention we have discovered that compounds of the type just referred to, as for example, 22-isoallospirostan-3fl, lla-diOl may be converted into the corresponding triacetate of Mu -furo- In the foregoing equation AC represents an acetoxy group although it may be understood that it may represent other lower fatty acid groups depending on the type of anhydride utilized in the reaction.

In practicing the reaction above outlined the sapogenin, i. e., 22-isoal1ospirostan-3p, 11u-diOl,iS dissolved in a,

suitable lower fatty acid anhydride such as acetic anhydride and heated in a sealed tube at a temperature of approximately 200 C., for arelatively long period of time such as;8 hours. Thereafter it is poured into .water,-purifiedandevaporated to drynessto give an oily residue. The oily residue of the stepjust referred to is then dissolved in a lower fatty acid such as acetic acid together with an organic solvent such as ethylene dichloride and asmall amount of water with heating until all of the oil is dissolved. The solution-is cooled to below room temperature as. for. example C., and treated slowly with stirring with a.solution.of chromicanhydride in acetic acid together with a-small amount of water. The mixture-isiallowedto. stand for a short period of time as for example 2"hours and the ethylene dichloride layer separated by decantation. The aqueous layer is then extracted with. a suitable solvent such as chloroform and the ethylenedichloride solution and chloroform'solution isrpurifiedand' combined- After evaporation the residue is dissolvedina mixed solvent such as benzene and hexane andchromatographed in an alumina column. The aluminacauses a mild saponification and the product is A i -allopregnene-3fl, llu-diol--one diacetate.

The A compound is then hydrogenated as by shaking with.hydrogen at room temperature and pressure together ,witha hydrogenation catalyst such as 10% pal ladium on barium sulphate. When the absorption of hydrogen ceased, .i. e., in approximately 1 hour, the catalyjstis filtered 01f. and the solution evaporated to dryness. The residue on recrystallization gave allopregnane-3fl, Ila-diol-ZO-one diacetate. From the diacetate of the previousstep the corresponding 17a-triol compound could then be prepared by'enolizing the allopregnan-3fi, lladio1-20-one diacetate as with a lower fatty acid anhydride such as acetic anhydride in the presence of a catalyst such as p-toluenesulphonic acid followed by oxidation with an aromatic per acidsuch as perbenzoic acid and saponification of the oxidation product under mild conditions, i. e., room temperature or below with methanolic alkali metal hydroxide such as sodium hydroxide. The resultant product, allopregnane-BB, 11a, 17a-triol-20-one may then be treated with a mild oxidizing agent to form allopregnan-3, 11, 20-trione-17u-ol which can be selectively hydrogenated as withvRaney nickel catalyst in alcohol solution to form'allopregnan-3fl, 17OL-dlOl-11, 20- dione; This process is outlined in the following equations:.

' The mild oxidizing-agent"indicated above may bean N halo acid amide preferably' -in pyridine such as N-bromoaeetamideor N-bromosuccinimid'er In'the alternative 4; two equivalents (1.32 mols) of chromic anhydride may be used under mild conditions. The resultant product of the above reaction is allopregnan-Zifi, 17at-di0l-l1, 20-dione which, as previously set forth, may be converted into di- 5 hydroallocortisone.

Allopregnan-3fl, 11a, l7a-triol-20-one may also be converted in to dihydr'oallocortisone-asexemplifiedby the following equation:

In the above equation AC represents the acetate radical, althoughother lower fatty acid esters may also be formed by the corresponding reagents.

In practicing the process steps above outlined the allopregnane-3fl, 11d, 17bc-triol-20-one is dissolved in a suitablesolvent and monobrominated to give the corresponding 21-bromo derivative which is in turn reacted with sodium iodide to give the corresponding 21-iodo compound which may be transformed with potassium acetate into the 2l-monoacetate as above indicated. Thereafter the 21-acetate is treated with a mild oxidizing agent of the type previously set forth, i. e., N-bromoacetamide or chromic anhydride under mild conditions.

The following examples serve to illustrate the present invention but are not intended to limit same:

Example I A -allofur0stene-3;3,11a, 26-triol triacetate.-A so lution of 5 g. of 22-isoallospirostan-3 3, lla-diol in 20 cc. of acetic anhydride was heated at 196 in a sealed tubeduring 8 hours and then poured in water. The mixture was extracted with ether and the ether solution was washed with water, sodium bicarbonate and water until neutral, dried over sodium sulphate and evaporated to dryness. 4.6 g. of an oily residue was obtained which was used for the next step without further purification.

Example 11 A -all0pregnene-3p, 11 oc-diOl-ZO-One diacetate.-4.6 g. of A -allofurostene-3 3, 11a, 26-triol triacetate obtained according to Example I were dissolved in a mixture of 45 cc. of acetic acid, 36 cc. of ethylene dichloride and 15 cc. of water, heating until all dissolved. The solution was cooled to 15 and treated drop by drop and with mechanical stirring with a solution of 1.4 g. of chromic anhydride in 2.2 cc. of water and 22 cc. of acetic acid.

After 2 hours standing at room temperature the mixture was poured in water and the layer of ethylene dichloride was'separated by decantation; The aqueous layer was extracted withichloroform and the combined chloroform andethylenedichloride'solution was washed several times with'water, "dried "over sodium sulphate and evaporated 5 to dryness. The residue was dissolved in a mixture of 50 cc. of benzene and 200 cc. of hexane and chromatographed in a column with 250 g. of alumina. The fractions eluted with benzene-ether (30:20 and 40: 10) were combined and evaporated to dryness. The residue crystallized upon digestion with a mixture ether-pentane to yield 1.6 g. of A -allopregnene-3fl, 11u-diol-20-one diacetate having ultraviolet absorption maximum at 238 ,u. (log 6 4.12).

Example III Allopregnanedfi, '11a-di0l-20-0ne .diacetate.A solution of 600 mg. of A -allopregnene-3B, 1loc-diOl-200ne diacetate in 100 cc. of ethyl acetate was shaken at room temperature and atmospheric pressure under an atmosphere of hydrogen with 115 mg. of 10% palladium on barium sulphate catalyst. The absorption of hydrogen ceased after one hour. The catalyst was filtered and the solution was evaporated to dryness and the residue was crystallized from hexane-acetone to give 510 mg. of allopregnan-3fl, lla-diol-20-one diacetate, which in contrast to the starting material, showed no selective absorption in the ultraviolet spectrum. Conventional saponification gave the free compound.

Example IV Allopregnan-3B, 11a, 17a-trial-20-0ne.-A solution of 2 g. allopregnan-3B, lloc-dlOl-ZO-ODC diacetate and l g. of p-toluenesulphonic acid in 170 cc. of acetic anhydride was slowly concentrated to a volume of 20 cc. in the course of 5 hours and then it was poured in ice water containing 3 cc. of pyridine. The product was extracted with ether, washed with2% sodium hydroxide and water until neutral, dried over sodium sulphate and evaporated to dryness. The residue was dissolved in hexane and passed through a column of washed alumina in order to eliminate impurities. The solution was concentrated to dryness to leave 2.15 g. of A -allopregnene-3/8, 11a, 20-triol triacetate which was not crystallized but directly dissolved in 20 cc. of chloroform and let to react during 40 hours at room temperature with 13 cc. of a chloroform solution of perbenzoic acid containing 63 mg. of acid per cc. The mixture was diluted with more chloroform and washed with sodium iodide, sodium thiosulphate, sodium carbonate and water,and concentrated to a small volume. The solution was then treated during 30 minutes at room temperature with 1 g. of sodium hydroxide in 100 cc. of methanol. After neutralizing with acetic acid the solution was concentrated to 30 cc. and diluted with water to obtain complete precipitation. The precipitate was collected and crystallized from ether containing a small amount of hexane, yielding 1.35 g. of allopregnan-3fl, 11a, 17a-triol-20-one having a melting point of 253 255 C., (at) -46 (chloroform).

Example V Allopregnan 17a l 3, 11, 20 tri0ne.-Meth0d A.-A solution of 113 mg. (1.32 mol) of chromic anhydride in cc. of acetic acid and 0.5 cc. of water was added drop by drop to a stirred solution of 300 mg. of allopregnan-Bfi, 11a, l7a-triol-20-one in 20 cc. of acetic acid maintained at 15. After 5 hours standing, the mixture was poured in water and the precipitate extracted with ether. The ether solution was washed until neutral and concentrated until crystallization started. After cooling the mixture, 150 mg. of crystalline allopregnan-l7a- 01-3, 1.1, 20-trione was obtained.

Method B.550 mg. of N-bromoacetamide were added to a solution of 300 mg. of allopregnan-3B, llu, 17a-triol- 20-one in 6 cc. of pyridine. After 40 hours standing at room temperature, the solution was diluted with 70 cc. of 1% hydrochloric acid. The precipitate was collected, washed, dried and recrystallized from ethyl acetate to give '255 mg. of allopregnan-17a-ol-3, l1, 20-trione identical to the one obtained according to Method A.

Example VI Allopregnan-3fl, 17-di0l-11, 20-di0ne.A solution of 200 mg. of allopregnan-17u-ol-3, l1, 20-trione in 20 cc. of ethanol was shaken at room temperature and atmospheric pressure under an atmosphere of hydrogen in the presence of 2 g. of previously reduced Raney nickel catalyst. After 1 hour the catalyst was filtered and the solution was evaporated to dryness. The residue crystallized from ether-hexane to yield 185 mg. of allopregna'n-BB, 17a-diol-11, 20-dione with a melting point of 270"- 272 C. l

' Example VII 21-br0m0-allopregnane-3,B, 11a, 17a-tri0l-20-0ne.A solution of 0.7 g. of bromine in 7 cc. of chloroform was slowly added to a stirred solution of 1.5 g. of allopregnan- 3,8, 17a-triol-20-one in 15 cc. of chloroform (no hydrobromic acid was added). After adding all the bromine, the solution was diluted with chloroform and well washed with water, dried over sodium sulphate and concentrated in vacuum at a temperature below 40. The residue crystallized from chloroform-ether to give 1.6 g. of 21- bromo-allopregnane-BB, 11cc, l7a-triol-20-one.

Example VIII Allopregnane-3/3, 11a, 17a, 21-tetr0l-20-0ne 21-m0n0- acetate.Without further purification, the bromo compound obtained according to Example VII was dissolved in 40 cc. of acetone and mixed with a solution of l g. of sodium iodide in 10 cc. of acetone. After refluxing for 10 minutes, the solution was filtered to remove the sodium bromide which had formed. The solution was diluted with hexane to a volume of 80 cc., mixed with a mixture of 7.5 g. of potassium bicarbonate and 4.5 cc. of acetic acid and the whole was refluxed during 10 hours. The mixture was concentrated to a volume of 20 cc., diluted with water and the precipitate formed was collected. After washing and drying, the precipitate was recrystallized from hexane-acetone, yielding 1.1 of allopregnan-Bfl, 11a, 17cc, 2l-tetrol-20-one 2l-monoacetate.

Example IX Allopregnane-Ua, 21-di0l-3, 11, ZO-trione 21-acetate (dihydroallocortisone acetate).Meth0d A.-A solution of 101 mg. of chromic anhydride in 5 cc. of acetic acid and 0.5 cc. of water was added drop by drop to a mechanically stirred solution of 300 mg. of allopregnan-3l3, 11:1, 21-tetrol-20-one 21-acetate in 20 cc. of acetic acid, at room temperature. After standing 16 hours, the mixture was poured in water and the precipitate extracted with ether. The ether solution was washed to neutrality, dried over sodium sulphate and concentrated until crystallization started. After cooling, the precipitate was collected to give 147 mg. of crystalline allopregnane-17a, 21-diol-3, l1, 20-trione 2l-acetate, melting point 234-237 C.

Method B.-620 mg. of N-bromoacetamide were added at room temperature to a solution of 300 mg. of allopregmane-313, 11a, 17a, 2l-tetrol-20-one 2l-acetate in 6 cc. of pyridine. After 48 hours the mixture was diluted with 70 cc. of 1% hydrochloric acid and the precipitate was filtered, washed, dried and recrystallized from ethyl acetate to give 263 mg. of allopregnane-l7a, 21-dio1-3, 11, 20-trione acetate, identical to the one obtained according to Method A.

We claim:

1. A process for the preparation of allopregnane-3B, 11oz, 17a-triol-20-one which comprises enolizing allopregnane-3fi, 1la-diol-20-one with acetic anhydride in the presence of p-toluenesulphonic acid, followed by oxidizing the enol acetate with an aromatic per acid and saponifying the oxidation product with methanolic sodium hydroxide under mild conditions.

2." Anew-compound consisting of allopregnane-ilfifl 1d,

References Cited in the fiI of this patent UNITED STATES PATENTS Marker- July 4, 1944 Sarett "Feb. 13, 1951 Kaufmann May 13, 1952 Murray Ju1y'8, 1952 Kendarl July 8, 1952 Gould Mar. 17, 1953 OTHER REFERENCES Fieser t 211.: Natural Products Related to Phenanthrene, 3rd ed., 1949, pp. 437, 456, 451, 457.

Chamberlain: JACS, vol. 72, p. 2396, May 1951, recorded April 26, 1951; 1 

2. A NEW COMPOUND CONSISTING OF ALLOPREGNANE-3B, 11A, 17A-TRIOL-20-ONE HAVING A MELTING POINT OF 253*-255* C. 